Refactor ByteArray from std::string alias to class implementation

[tlifschitz]

• Converted ByteArray from an alias of std::string to a class implementation.
  • Added multiple constructors to support initialization from various sources:
  • std::vector
  • uint8_t pointer with size
  • std::string
  • C-string with and without null termination
  • Implemented static methods fromHex() to construct from hex strings.
  • Overloaded the stream operator to support pretty printing ByteArrays.
• Create common code directory to be shared among simpleble and simplebluez
• Use new ByteArray class instead of std::vector in simplebluez

[tlifschitz]

@kdewald pls review

[CLAassistant]

All committers have signed the CLA.